The instantly recognizable APX soundhole thickens lower-mid response and gives a more strident, open low end.

System 66 features an under-saddle piezo pickup developed by Yamaha. Controls include a 3-band equalizer, an adjustable mid-range frequency control,and a precision chromatic tuner for optimum sound tailoring. The system is powered by easy to obtain AA-size batteries that provide a stable power supply for improved sound quality.